Torque limiting wrench



May 17, 1960 J. HOSTETTER TORQUE LIMITING WRENCH Filed Dec. 26. 1957 z 0 J 1 W yr 4 Z 9A r x 4 M C W i 2 i M m l. i1.

Unit States Patent TORQUE LIMITING WRENCH John L. Hostetter, Tucson, Ariz., assignor to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Application December 26, 1957, Serial No. 705,457

2 Claims. (Cl. til-52.4)

This invention finds particular utility in the field of tools, relates generally to wrenches and relates more specifically to a particular embodiment of a torque limiting wrench.

In many industrial manufacturing situations, it has been found desirable to employ torque limiting wrenches'in the final securing and positioning of threaded members such as bolts, nuts, threaded fittings and like structures. In order to prevent the possibility of overstressing either the threaded members or objects being secured thereby, or to insure equal and consistent torque application to numerous cooperating threaded elements, it is desirable that a torque limiting type of wrench be employed. Torque limiting wrenches have heretofore assumed many forms and have been adapted for the application of torque of magnitudes up to several hundred foot-pounds. These prior torque type wrenches have included flexible handles coupled with sockets or socket adapers and/or open ended wrenches and have been both fixed and adjustable. Additionally, indications of torque limits have been provided by comparative application with springs or other structures of known forces positioned at different lengths from the point of such torque application. Torque indications have also been provided through the use of dials, levers, indicators and over center snap mechanisms. Additionally, some types of heretofore known torque wrenches are usable in blind areas, with an indication of torque limit being provided by an audible signal.

In most prior instances, torque type wrenches, adapted particularly for use in connection with the assembly of machinery, have been complex in manufacture and, accordingly, relatively expensive. These wrenches have also necessarily been relatively large, in order to permit universal use thereof and have not been satisfactory for use in assembling small objects having limited accessibility as may be found in apparatus such as in aircraft and guided missile devices. However, in such devices, the

delicate nature of some of the components requires the use of wrenches by production mechanics that will enable easy access to such components, a firm gripping of the component whether it be a nut or a knurled fitting, and torque application to a predetermined limit. 'Additionally, in high production situations, it has become necessary to employ a considerable number of like torque limiting wrenches and the cost of manufacture or purchase of the wrenches has also become a factor, especially in instances where only a moderate amount of torque is required.

In most production situations of the type described hereinbefore, it has been the standard procedure to employ either finger tightening, pliers, or a conventional torque wrench and adapter to secure components in position. Obviously, the finger tightening technique is inadequate, pliers and other similar tools tend to damage the surfaces of the nuts or fittings on which they are used and conventional types of torque wrenches are too large and cumbersome for use in these particular situations.

It is accordingly one object of the present invention to provide a novel torque limiting wrench.

It is another important object of the invention to provide a miniature torque limiting wrench that is essentially unitary and extremely simple in construction and operation.

Still another object of the invention is to provide a novel torque limiting wrench that is light in weight, relatively small in size, reliable and effective in use and economical in manufacture.

A still further object of the invention .is to provide a novel torque limiting wrench that is adaptable to a variety of sizes of objects to which torque is to be applied without the necessity for changing jaws, sockets, fittings or the like, and which may be used for torquing and/ or untorquing, as desired.

Other and further important objects of the invention will become apparent from the disclosures of the following detailed specification, appended claims and accompanying drawing, wherein:

Figure l is a perspective view of the torque limiting Wrench of the present invention;

Fig. 2 is a perspective view showing a typical use of the present torque limiting wrench;

Fig. 3 is an enlarged fragmentary, partially sectional view of the torque indicating portion of the present wrench; and

Fig. 4 is a view similar to Fig. 3 showing the wrench portions in different positions.

With reference to the drawing, the torque limiting wrench hereof is shown as indicated generally at 10 and includes a unitary body structure 11. It is to be noted that the body structure is constructed generally from one piece of material which may be one of many known types of metal having resilient characteristics, such as steel, brass, an aluminum alloy or the like. The body 11 may be stamped, cut, molded or otherwise formed from such material to provide the present desired configuration.

The unitary body 11 includes a pair of integral arm portions 12 and 13, the arm portion 12 having an end portion 14 disposed substantially normal thereto and the arm portion 13 being integrally connected to a handle portion 15 as by an interconnecting portion 16. Additionally, the arm portions 12 and 13 are integrally joined by means of an interconnecting portion 17, and an extension portion 18 is positioned contiguous with the arm portion 12. The arm portion 12, together with the extension portion 18, the arm portion 13 and the handle portion 15, all lie in normal substantially parallel relationship with the portions 12 and 13 and handle portion 15 forming a substantially S-shaped configuration. It is to be noted that the interconnecting portions 16 and 17 are suitably contoured into the adjacent portions of the arms and handle, in order to provide the desired flexibility as between the portions of the body structure and a smooth distribution of stresses thereabout.

The arm portion 13, together with its integral interconnecting portion 16 with the handle 15, serves to support a jaw 20 that may be formed from a hardened ma terial and may be disposed in a suitable reduced width area of the interconnecting portion 16. The jaw 20 may be secured in position by means of a laterally disposed pin 21 which extends through the body, with an outer surface thereof being provided with suitable jaw face serrations 22. The end portion 14 of the arm portion 12 is also provided with a jaw 23 that is similarly disposed relative to the end portion and retained in position by means of a pin 24. The jaw 23 may also be provided with suitable jaw face serrations 25.

As shown in Figs. 1, 3 and 4, the free end of the handle portion 15 carries an integral .block portion 26 disposed 3 r therefrom and generally normal thereto, with a free end of the block 26 being normally contiguous with an outer surface of the extension portion 18. The block portion 26 has a bore 27 which also extends through the integral area of the handle portion 15. As shown, a pin orsc'rew 28 is slidably disposed in the bore 27 and has a head 30 thereon. The axis of the screw 28 is disposed substantiab ly parallel to the serrated surfaces of the jaws 2 and 23'. The screw 28 also threadably supports a nut 31, the inner surface of which is adapted to engage an outersu'rface 32 of the handle portion 15. The head 30 of the screw 28 is spaced from an outer end surface 33 of the block portion 26, there being a compression spring 34 disposed about the shank of the screw 28 and between the head 30 thereof and the surface 33 of the block portion 26.

In use of the present torque limiting wrench, the jaws 20 and 23 are opened by grasping the wrench and compressing the extension portion 18 toward the handle portion 15. The resiliency of the various portions 'of the integral body structure serves to permit this action and serves thereby further to displace the engaging surfaces of the jaws 20 and 23 at a greater distance apart than that of their'normal state. The jaws 20 and 23 may then be placed about an object to which torque is to be applied as, for example, a fitting indicated at F in Fig. 2, and torquing force may be applied thereto by application of such force by engagement of a hand or finger with the outer surface of the head 30 of the screw 28. This action serves slightly to separate the extension portion 18 from the handle portion to effect a tighter grip as between the surfaces of the jaws and 23 and the object engaged by the jaws. The torquing force is continued until such time as the force of the spring 34 is overcome, an indication of this limit having been reached being provided, as shown in Fig. 4, by slidable movement of the screw 28 in the bore 27 and separation ofthe inner surface of the nut 31 from the surface 32 of the handle 15. When this separation occurs, a preset and/or predetermined torque limit has been reached, this limit having been determined by the disposition of the nut 31 along the threaded portion of the bolt 28 and initial static compressive force established on the compression spring 34.

Following establishment of the desired-torque upon the object to which torque is being applied, the extension portion 18 and the handle portion 15 are again grasped and moved toward each other whereby to open the jaws 20 and 23 and release the wrench from the fitting F.

It may thus be seen that the torque limiting wrench hereof is extremely simple in construction and that the lateral thickness and width thereof are such as to enable use of the tool in areas of limited accessibility. Repeatable torque limits may thus be established on nuts, bolts o'r fittings through'use of the present tool and over a wide range of various sizes of such objects. For disconnecting use of the present torque limiting wrench, it is only necessary that the wrench be turned over from the position shown in Fig. 2 and that operation thereof be reversed from that described in connection with the torquing operation.

Having thus described the invention and the present embodiment thereof, it is desired to emphasize the fact that many-modifications may be resorted to in a manner limited only by a just interpretation of the following claims.

I claim:

1. In a torque limiting wrench, the combination of: a unitary body structure; a pair of opposed elongated jaw portions disposed at a slight angle to each other and carried by said structure; integral resilient arm portions in said body structure and interconnecting said jaw portions; an integral handle portion also in said body structure and extending from one of said jaw portions, said arm and handle portions being disposed in a generally S- haped configuration; a pin slidably carried by the free end of said handle portion, said pin having enlarged portions on each end thereof; and a compression spring disposed about said pin and positioned between a lateral surface of said handle portion and an enlarged portion of said pin, the axis of said pin being disposed generally parallel to said jaw portions, said jaw portions being adapted for wedge engagement with an object, torque, being applied to said object through said jaw portions by slight movement thereof toward each other and by application of force to one enlarged portion of said pin, movement of said pin relative to said handle portion by a force greater than the force of said compression spring providing an indication of torque limit being applied to said object.

2. In a torque limiting wrench, the combination of: a unitary b'ody structure; a pair of opposed elongated jaw portions disposed at a slight angle to each other and carried by said structure; integral resilient arm portions in said body structure and interconnecting said jaw portions; aninte'gral handle portion also in said body structure and extending from one of said jaw portions, said arm and handle portions being disposed in a generally S-shaped configuration; a pin slidably carried by the free end of said handle portion, said pin having a head on one. end and a threadably engaged nut on the other end to define enlargements thereon; a compression spring disposed about said pin and positioned between a lateral surface of said handle portion and the head of said pin, the axis of said pin being disposed generally parallel to said jaw portions, said jaw portions being adapted for wedge engag'ernerit with an object, torque being applied to said object through said jaw portions by slight movement there of toward each other and by application of force to said head of said pin, movement of said pin relative to said handle portion by a force greater than the force of said compression spring providing an indication of torque limit being applied to said object; and a free ended extension disposed integrally from one of said arm portions and positioned generally parallel to said handle portion.

References Cited in the file of this patent UNITED STATES PATENTS 1,328,389 Norwood Jan. 20, 1920 1,733,642 Beduorz Oct. 29, 1929 1,809,087 Watrous June 9, 1 931 2,560,716 Bortle et al. July 17, 1951 FOREIGN PATENTS 399,901 Great Britain Oct. 19, 1933 897,420 France May 22, 1944 OTHER REFERENCES Article: Simple Torque Wrench Made from Scrap Steel Parts, by Gerhard Wenke, in the American Machinist, July 28, 1949, page 104.

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